Magnesium alloy



United States Patent 2,822,267 Patented Feb. 4, l 95 21; Melting may be donein -a suitable crucible-with the protect1on-from atmospheric attack of a covering of a 2,822,267 saline flux free from magnesium chloride, A saline flux I V v I composed of 57 parts of;KCl, 28 parts of CaCl 12.5 GNE M ALLOY 5 parts of BaCl and 2.5 parts of c n, by Weightis silit'able George Fqe teg, Midl d, W assignor to Th Dow for use in the melting and alloying operation. After the Chemical Company,lvfi h ge ef fien bf metals are melted together,- the resulting alloy may be Delaware rflefined by stirring the molten alloy with additional saline N i ux. The so-refinedalloy is allowed to settle and after Drawing s 'gg gg ggxggi 1955 settling is separated from the flux as by decantation and e run into a suitable casting mold, e. g. a slab mold for 4 Claims. (Cl. 75168) rolling stock or an ingot mold for extrusion,

A preferred range ofproportions of the alloying metals 7 is; zinc 0.5 to lpe rcent, zirconium 0,5 to 0.7 percent, The invention relat t magnesiumbasesanoys. It thorium 0.3 to 0.7 percent, and rare earth metal 0.4 to m Particularly concerns an nPI W d magne iu 0.8 percent, e. g. misch metal. A desirable specific alloy base alloy containing thorium, zinc, and zirconium. formulation Within the scope of the invention is one Attempts to produce magnesium-base alloys containing having p n o um, -8 p rc of zinc, -6 thorium, zinc, and zirconium have not met with much P c Zirconium. the balance being m u commercial success due at least in part to the high In Sheet form as Produced y l n cast slab of thorium content heretofore .proposed. which makes the thesalloys the alloy possesses static n e Properties at alloys excessively costly without achieving the most deat least as 80 n h y eases better sirable combination of mechanical properties. It has than, anymasnesium-bsse 51191331103 heretofore known now been discovered th b ding h m containing thorium, zinc, and zirconium but without the sium-base alloy of small amounts of the alloying metals high thon'um content of conventional magnesium-base thorium, zinc, zirconium, and rare earth metal an excep- 3' Its secondary p p such as formahility, tional combination of extreme lightness, high strength, toughness, y, Weldahility, and Corrosion resisthigh resistance to corrosion and other desirable properties ahee, are superior to any known magnesium-base alloy is obtained. The invention then consists of the improved containing larger amounts thorium. Zine. Zirconium, magnesium-base alloy herein described and particularly so and rare earth metal example, the Corrosion pointed out in the claims. sistance as measured by the weight loss in the conven- In compounding the alloy, there is melted together tional alternate immersion test in 3 percent aqueous enough of the alloying metals to provide an alloy con- Sodium chloride solution at 95 F. for 14 days is at least taining in parts by weight, from 0.2 to 1.2 percent of as g as g P y magnesium, the Weight loss is zinc, 0.4 to 0.8 percent of zirconium, and from 0.1 to n t greater than about 0.2 milligram per square centi- 0.75 percent of thorium, 0.1 to 1 percent of rare earth meter per day in the said test. The trace of attack which metal, and magnesium in amount suflicient to make up occurs during the corrosion rate test in 14 days is quite the balance. From the foregoing proportions of the uniformly distributed over the surface of the metal. metals in the alloy, it is manifest that the alloy contains Alloys within the scope of the invention having a zinc at least about 96.45 percent of magnesium except for the content of 0.2 to 0.7 are cold-rollable to foil thickness, small amounts of impurities normally present in cornmere. g. 0.003 inch from sheet 0.125 inch thick, without an cial magnesium, say 0.1 to 0.3 percent by weight, when intermediate anneal. the alloy contains the maximum amounts of the other The alloys of the invention find their greatest useful metals. Similarly, the maximum amount of magnesium ness in applications requiring high strength both at room which is present when the other metals are present in temperature as well as moderately elevated temperature, their smallest proportions is 99.2 percent. Because of the e. g. up to 600 F. relatively high magnesium content of the alloy, it pos- The following examples which are set forth in the sesses substantially the same lightness characteristic of accompanying table are illustrative of the invention.

Properties Allrlo Oomposttlon F. 400 F. 600 F.

Percent Percent Percent Percent Percent TYS CYS TS Percent TYS TS Percent TYS TS Zn r RE Th E E E 1 0.5 0.6 0.5 0.3 4 37 as 44 10 27 20 42 14 16 2 1.0 0.6 1.0 0.5 5 37 36 45 15 27 30 so 13 15 3 1.0 0.6 0.5 0.5 6 36 36 44 22 24 2s 64 13 13 4 0.6 0.6 0.5 0.5 6 33 I 34 42 14 25 2s 4s 13 13 1 Strength given in nearest 1.000 lbs. per square inch of rolled test specimens. TYS=Ten ile yield strength at 0.2 percent deviation from the modulus line. CYS=Compressiou yield at 0.2 percent deviation from the modulus line.

The alloy of the invention is readily rolled hot from 5 any thickness of suitable rolling stock to desired gauge.

In preparing the alloy for rolling the melt of the desired alloy may be cast into slabs. The cast slabs are then scalped to remove the surface skin in which impurities usually collect. The scalped slabs may then be heat treated, as by soaking at 800850 F. for 8 hours. Hot rolling is commercial at 800 to 850 F. and when the temperature of the metal falls to between about 650 and 700 F. the rolled metal, if not reduced to the desired gauge, is reheated to 800-850 F. and rolled again. This procedure is repeated until the desired thickness is obtained. Following hot rolling, the rolled metal may be annealed at 800-850 F. audthen cold rolled at 1 to 2 percent reduction in thickness per pass to as much as 40 percent total thickness reduction at room temperature. A final anneal may be given after cold rolling depending upon the temper desired. A hard temper is obtained by heating for 1 hour at 500 F. a soft temper by heating for 1 hour at 800 F.

Since zirconium is somewhat difilcult to alloy with magnesium, instead of using zirconium itself, it is preferable to use as a source of the zirconium a zirconium rich magnesium-zirconium alloy in making the alloy of the invention. Zirconium which is effectively alloyed with the metals in the alloy is that which will dissolve in hydrochloric acid on subjecting a specimen of the alloy to the dissolving action of the acid. Unalloyed zirconium remains undissolved in this test.

I claim:

1. A magnesium-base alloy consisting of 0.2 to 1.2 percent of zinc, 0.4 to 0.8 percent of zirconium, 0.1 to 0.75 percent of thorium, 0.1 to 1 percent of rare earth metal selected from the group consisting of cerium, lanthanum, praseodynium, neodymium, and misch metal, the balance being magnesium, the zirconium in the said alloy being soluble in hydrochloric acid on subjecting the alloy to the dissolving action of the acid.

2. An alloy according to claim 1 in which the rare earth metal is misch metal comprising to percent of cerium.

3. A magnesium-base alloy containing 0.5 to 1 percent of zinc, 0.5 to 0.7 percent of zirconium, 0.3 to 0.7 percent of thorium, and 0.4 to 0.8 percent of misch metal, the balance being magnesium, the zirconium in the said alloy being soluble in hydrochloric acid on subjecting the alloy to the dissolving action of the acid.

4. A magnesium-base alloy containing about 0.8 percent of zinc, 0.6 percent of zirconium, 0.5 percent of thorium, 0.6 percent of misch metal, the balance being magnesium, the zirconium in said alloy being soluble in hydrochloric acid on subjecting the alloy to the dissolving action of hydrochloric acid.

References Cited in the file of this patent V UNITED STATES PATENTS 2,604,396 Jessup July 22, 1952 2,703,753 Nelson Mar. 8, 1955 OTHER REFERENCES Ser. No. 369,749, Sauerwald (A. P. 0.), published June 16, 1943. 

1. A MAGNESIUM-BASE ALLOY CONSISTING OF 0.2 TO 1.2 PERCENT OF ZINC, 0.4 TO 0.8 PERCENT OF ZIRCONIUM, 0.1 TO 0.75 PERCENT OF THORIUM, 0.1 TO 1 PERCENT OF REAR EARTH METAL SELECTED FROM THE GROUP CONSISTING OF CERIUM, LANTHANUM, PRASEODYNIUM, NEODYNIUM, AND MISCH METAL, THE BALANCE BEING MAGNESIUM, THE ZIRCONIUM IN THE SAID ALLOY BEING SOLUBLE IN HYDROCHLORIC ACID ON SUBJECTING THE ALLOY TO THE DISSOLVING ACTION OF THE ACID. 